1. Field of the Invention
The present invention relates to a magnetoresistance effect element and a magnetic storage using same in which a switching current density in a spin-transfer magnetization switching can be reduced, and which enable the spin-transfer magnetization switching to be performed without causing breakdowns of a memory element which uses a tunnel magneto resistance (hereinafter referred to as a TMR, an abbreviation of Tunnel Magneto Resistance), and of a selection element (e.g. a field effect transistor (hereinafter referred to as a FET, an abbreviation of Field Effect Transistor)).
2. Description of Related Art
In a conventional magnetic storage, magnetization switching of a magnetoresistance effect element is operated by a current-induced magnetic field induced from a current line which is disposed electrically separated from the magnetoresistance effect element, and which is one of current lines which are intercrossing three-dimensionally (e.g. orthogonally intercrossing) with the magnetoresistance effect element being interposed therebetween (refer, for example, to patent document 1). However, there has been such a problem that if the size of a memory cell is reduced in order to increase its capacity, a switching magnetic field will increase abruptly, and in conjunction therewith, also, a required current will increase abruptly. Further, there is another problem that if the size of a memory cell is reduced smaller than 200 nm φ,which will be necessary in order to realize a super gigabit scale (G bit) capacity, a value of current required for writing will exceed an upper limit of allowable current density in wiring, thereby inhibiting any further writing.
In contrast, in a magnetic storage using the spin-transfer magnetization switching, there is such an advantage that the smaller the size of a memory cell becomes, a current required for magnetization switching becomes smaller, which is suitable for manufacture of an extra large capacity magnetic storage (refer to, for example, patent document 2).                [Patent Document 1] JP-Patent Application Publication No.2002-246566        [Patent Document 2] JP Patent Application Publication No.2003-48614        
A problem to be solved by the present invention is that because a current density required for the spin-transfer magnetization switching is at present more than 1×10 MA/cm2, there occur breakdowns of a switching element using a TMR film, and of an element selection FET or the like. Although it is reported to have decreased a switching current by reducing the size (area) of a memory cell, there still remains a problem that because of an increase in the resistance in the element due to a reduced area of the memory cell, a required voltage for switching which is a product of the current and the resistance cannot be reduced. It is also reported that because of the necessity of reducing the current density for switching, the cell size is fabricated in the order of several, m to provide multiple magnetic domains, and to actuate magnetization switching by use of a current-induced magnetic field produced by a current perpendicular to the plane of the film, thereby enabling the magnetization switching to be performed at a current density in the order of 1 MA/cm2. However, because of its switching current being as large as several tens mA, and because of its cell size increasing substantially, there is a problem that the memory cannot yet have a very large capacity.